Devices for utility locating include transmitter antennas having magnetic cores of ferromagnetic material for use with coils, current sources, and/or other components generate and send magnetic field signals. One type of such device is known as a sonde or beacon. Sondes or beacons typically include a power supply, current signal source, and amplifier along with a dipole magnetic field antenna. Transmitted magnetic field signals may be continuous wave (CW) signals or, in some applications, may include encoded data or information or other signal modulation.
Signals from sondes, beacons, and similar devices may be used to transmit magnetic dipole fields at one or more frequencies and/or to send data to other utility locating system devices via transmitted magnetic field signals. Utility locators may be used to locate the sonde underground or within a cavity or opening by sensing the generated dipole magnetic field, typically at the ground surface. For example, a sonde deployed into an underground pipe on the end of a push-cable can generate a magnetic field signal that can be sensed by an above ground user with a utility locator, typically directly above the sonde's underground location. This application is a type of utility locating operation, also known as a “locate.”
In related applications, a sonde may be combined with a video or still camera on the end of a push-cable, allowing the location of the camera under the ground to be determined in the locator, and the corresponding ground surface location (e.g., in latitude/longitude coordinates or other reference positions on the ground surface) to be associated and stored with an image or video captured within the pipe or cavity. Pipe characteristics or features, such as breaks, invasions of roots, corrosion, branches, etc. as shown in the images or video may then be precisely associated with surface positions or coordinates, and corresponding maps showing pipe features under the ground may be generated from collected data.
Antenna and magnetic cores known in the art for these applications typically rely only on a jacket wrapped about a core. The jacket provides a force to return the antenna to a straightened position after flexing, which is typically minimal. However, existing antennas and cores are limited in the amount of packing of ferromagnetic core material, as well as ability to flex and then self-straighten, thus reducing the overall effectiveness of the antenna. For example, limits in flexibility restrict the type of openings a sonde can be pushed through, and bends or obstructions in pipes may further limit sonde deployment. Moreover, when a core is bent, the magnetic field strength decreases, and if the core cannot readily self-straighten to return to its initial shape, the magnetic field signal strength may continue to be reduced until the core is returned to its non-flexed shape.
Accordingly, there is a need in the art to address the above-described as well as other problems.